The Yard Guys

[neilpride]

Thats quite simple Smack, maybe that Passport got a keel stub and proper glassed masive beams and stringers to spread loads, those flat hulls holding thousands of iron pounds without a real good structure are not grounding friendly,, is not the first Jeaneau with a hull cracked after a grounding....

[Exile]

Why do you assume that groundings & hitting stuff aren't a reasonably foreseeable part of bluewater cruising, even for accomplished & experienced sailors? Collision bulkheads and watertight compartments are not limited to aluminum, high latitude "expedition" boats. Boats like Amel's & Calibers have them too. Maybe it's overkill for most, but you can argue that airbags in your car are too. Maybe it's an image thing -- you know, not "cool" to contemplate the downside of going "fast."

Originally Posted by smackdaddy

This boat "survived it" too apparently. As I pointed out above, we're really talking about the extent of the damage.

Yes, we are, and the repair costs that go along with that. You mean that the fact that the Jeanneau didn't just sink makes the build "good enough" for bluewater cruising? Maybe I'm not understanding the point you're trying to make.

But two questions here:

1. In terms of the type of force that will be applied in a grounding, how is your Passport 47 different than these boats...or even this Oyster 72...




Passport 47:



2. Are you absolutely certain there was literally NO damage or "fatigue" to the glass in the hull, the keel/keel-structure, the stiffeners, the tabbing, etc.? If so, how?

A good, thorough survey I suppose. So are you saying that you're better off with more damage because it can be more readily seen??

[Polux]

Originally Posted by smj

Wouldn't the heavier stronger boat have more inertia when hitting the rock than the lighter boat? May cause similar damage.


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yes, the heavier the boat, the bigger the energy on the impact. If it was a rock, it would certainly have damaged the lead, as it damaged on the Dockhead's Moody. The results of an hard growding on the boat structure are not necessarily visible and those are the worse ones. I remember some years back a beautiful, very expensive and well built Sweden yacht that lost the keel on an Atlantic crossing. It was know after that the boat had suffered a very hard growding but as the damage was superficial and apparently there was no structural damage they repaired only what they could see. Big mistake.

Today there are sophisticated tools. I have a friend, a sophisticated yard guy that is on the process of patenting a new more evolved system based on medical devices. He use it on my boat when I suffered a lateral blow from a 55T motorboat going fast astern, to see if there was internal delamination on both sides of the core and the images were pretty amazing, you could saw like if you were looking at a photo of a cut on the hull. That one does not understand why someone wants to cross an Ocean on an old Amel

[smj]

Originally Posted by Polux

yes, the heavier the boat, the bigger the energy on the impact. If it was a rock, it would certainly have damaged the lead, as it damaged on the Dockhead's Moody. The results of an hard growding on the boat structure are not necessarily visible and those are the worse ones. I remember some years back a beautiful, very expensive and well built Sweden yacht that lost the keel on an Atlantic crossing. It was know after that the boat had suffered a very hard growding but as the damage was superficial and apparently there was no structural damage they repaired only what they could see. Big mistake.



Today there are sophisticated tools. I have a friend, a sophisticated yard guy that is on the process of patenting a new more evolved system based on medical devices. He use it on my boat when I suffered a lateral blow from a 55T motorboat going fast astern, to see if there was internal delamination on both sides of the core and the images were pretty amazing, you could saw like if you were looking at a photo of a cut on the hull. That one does not understand why someone wants to cross an Ocean on an old Amel

Would that be thermal imaging?


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[Polux]

Originally Posted by smj

Would that be thermal imaging?

I believe it has more to do with ecography.

[Zach]

Alright yard guys, show of hands how many externally ballasted fiberglass boats you've seen with a loose keel...

Edit: Traditional full keel or cutatway forefoot...

I've only seen one, and that was courtesy of a hurricane and a rock jetty... Not a grounding.

Zach

[neilpride]

Originally Posted by Zach

Alright yard guys, show of hands how many externally ballasted fiberglass boats you've seen with a loose keel...

I've only seen one, and that was courtesy of a hurricane and a rock jetty... Not a grounding.

Zach

I never see one....

[neilpride]

This is very very interesting...

http://www.boatdesign.net/forums/att...tion-study.pdf

[avb3]

Originally Posted by neilpride

This is very very interesting...

http://www.boatdesign.net/forums/att...tion-study.pdf

I scrolled through it, but to be honest, I could not draw an conclusion out of it that would be useful to me.

What did you see in it that was important?

[smackdaddy]

Originally Posted by Exile

Why do you assume that groundings & hitting stuff aren't a reasonably foreseeable part of bluewater cruising, even for accomplished & experienced sailors? Collision bulkheads and watertight compartments are not limited to aluminum, high latitude "expedition" boats. Boats like Amel's & Calibers have them too. Maybe it's overkill for most, but you can argue that airbags in your car are too. Maybe it's an image thing -- you know, not "cool" to contemplate the downside of going "fast."

I fully assume groundings and even hitting stuff is a foreseeable part of bluewater cruising. After all, aren't several production boats doing things like kevlar reinforcement in hulls (e.g. - Hunter)?

I'm just saying being "surprised" at damage from striking a rock at hull speed - or, worse, assuming there "should be none in a 'real boat'" - is a little strange. And trying to say that this represents poor construction in any way is a serious stretch.

[neilpride]

Originally Posted by avb3

I scrolled through it, but to be honest, I could not draw an conclusion out of it that would be useful to me.

What did you see in it that was important?

Page 9, cant copy paste from the report.

[smackdaddy]

Originally Posted by Zach

Alright yard guys, show of hands how many externally ballasted fiberglass boats you've seen with a loose keel...

Edit: Traditional full keel or cutatway forefoot...

I've only seen one, and that was courtesy of a hurricane and a rock jetty... Not a grounding.

Zach

How many builders are still doing those these days?

[Cheechako]

Originally Posted by smackdaddy

I fully assume groundings and even hitting stuff is a foreseeable part of bluewater cruising. After all, aren't several production boats doing things like kevlar reinforcement in hulls (e.g. - Hunter)?

I'm just saying being "surprised" at damage from striking a rock at hull speed - or, worse, assuming there "should be none in a 'real boat'" - is a little strange. And trying to say that this represents poor construction in any way is a serious stretch.

That's really the heart of it isn't it? two camps......
The one I'm in fully expects to be able to hit a rock with the hull or keel and have little if any damage and also believes a boat that typically wont DOES represent poor construction.
After all... even today's cars are suppose to survive 5 mph without damage as I remember..... water absorbs a lot of energy

[avb3]

Originally Posted by neilpride

Page 9, cant copy paste from the report.

You mean this:

It is not possible to relate the speed directly to grounding force and in any case this would be meaningless as a low speed impact on rock may be more damaging than a high speed impact on mud. The mechanics of impact of yachts with containers, berg-bits or whales defies simple analysis. Solid mechanics would need to be factored in - quite inappropriate for a simple standard. This is a crude deterministic approach to a probabilistic load case and should be treated with caution.

Notwithstanding this, to give a feel only for the effective decelerating force (applied at the centre of gravity) implied by 0,8g (10m boat) or 1.1g (20m boat), assuming a constant impulse approach, a boat travelling at the hull speed would stop in about 0.5 second (translation only).

The load applied at the keel would cause a bow down attitude of (very roughly) 0.5m at the bow. This all seems to constitute a pretty severe load case. Please note again – very rough figures.

It emerged from the validation that some boats, particularly those with no girders had little hope of complying with this load case, without substantial local reinforcement.

It is important to recognise differences between the risk/consequences of impact loads on ocean racing boats with those of typical recreational craft. Hence, it was felt sensible to have a dual grounding load case approach; NORMAL and ENHANCED. Designers/builders could opt for either.

A category A or B yacht need not necessarily be designed to impact Type II. It is for the designer or builder to decide. Type II may be applicable to ocean-going racing yachts in collision with floating objects, ice flows or marine creatures. For other category A or B craft (while designed to the appropriate requirements in all other respects) such a load case may not be appropriate. Whatever type is selected, the following note shall be included in the owner’s manual to the effect: ‘This boat has been designed to a Impact Type [I] [II] (delete as necessary) grounding scenario as defined in ISO-12215-9, where the craft is expected to be operating at [low] [high] speed prior to the impact (delete as necessary). While compliance does not guarantee that the boat will suffer no damage in such a grounding, the resistance of a boat designed to Type II is normally expected to be substantially greater than that designed to Type I’.

[smackdaddy]

Originally Posted by Cheechako

That's really the heart of it isn't it? two camps......
The one I'm in fully expects to be able to hit a rock with the hull or keel and have little if any damage and also believes a boat that typically wont DOES represent poor construction.
After all... even today's cars are suppose to survive 5 mph without damage as I remember..... water absorbs a lot of energy

Again, all boats we've been discussing take these things into account. From there much of it depends on speed and force of the collision. Did you look through the report Neil linked to? Your assumptions could very well be a little off.

Regardless, the danger is in assuming that no damage occurred...even if you don't see it.